1. Field of the Invention
The present invention relates to a substrate processing unit.
2. Description of the Related Art
In a photolithography process, for example, in semiconductor device fabrication processes, resist coating treatment for forming a resist film on a surface of a wafer, exposure processing for performing exposure by irradiating the wafer in a pattern, developing treatment for developing the wafer after the exposure, heat treatment and cooling treatment before the coating treatment, before and after the exposure processing and after the developing treatment, and so on are performed, and these treatments are performed in various kinds of processing units of a coating and developing treatment system.
For example, cooling treatment before the coating treatment is performed in a manner that the wafer is mounted on a cooling plate provided in a casing for a predetermined period to be cooled to a predetermined temperature, for example, 23xc2x0 C. A cooling unit in which such a cooling treatment is performed is provided with an exhaust means for removing impurities, which are produced from the wafer or the like, by sucking an atmosphere in the casing, and therefore the pressure in the casing is lower than that outside the casing. Further the casing is provided with a transfer port through which the wafer is carried in/out, and the transfer port is provided with a shutter for opening and closing the transfer port to keep a predetermined atmosphere within the cooling unit.
In the coating and developing treatment system, air for keeping a clean atmosphere therein is supplied to form a descending current. As the air in this event, the atmosphere in a clean room in which the coating and developing treatment system is located is used, and the temperature of the air when supplied is the same as that in the clean room, for example, 23xc2x0 C. In the coating and developing treatment system, however, a number of heat treatment units where heat treatment is performed are provided, and thus the temperature of the air varies in the coating and developing treatment system by heat from these heat treatment units.
Further, a carrier for carrying the wafer between the various kinds of processing units including the cooling unit is provided in the coating and developing treatment system, and when the carrier carries the wafer into/out of the cooling unit, the aforesaid shutter of the casing is opened to pass the wafer through the transfer port.
As described above, however, since downflow is formed in the coating and developing treatment system and a negative pressure is formed in the cooling unit, the air in the coating and developing treatment system flows into the cooling unit when the shutter of the cooling unit is opened. Further, the temperature of the air flowing in is different from that of the wafer, and thus when the wafer for which cooling treatment has been finished is carried out, the temperature of only a part of the wafer close to the transfer port varies due to the air flowing in.
As a result, unevenness occurs in temperature distribution within a plane of the wafer. The wafer in this state is carried to the resist coating unit and coated with a resist solution thereon, which leads to the fact that the resist solution is applied onto the wafer having uneven temperatures, causing unevenness in thickness of the resist film. Consequently, resist films having a predetermined thickness cannot be obtained, resulting in decreased yields.
The present invention is made in consideration of the above-described aspects, and its object is to provide a substrate processing unit which restricts flow of gas into a processing unit such as a cooling unit or the like, the flow of which causes unevenness in temperature within a plane of a wafer or the like.
In order to achieve the above object, the substrate processing unit of the present invention is a processing unit for processing a substrate in a casing, having: a transfer port provided in the casing, through which the substrate passes when the substrate is carried into the casing by a carrier for carrying the substrate; and an inflow restricting device for controlling an atmosphere outside the casing to restrict the atmosphere from flowing into the casing through the transfer port.
According to the invention, since the inflow restricting device is provided, it is possible to control a flow of the atmosphere outside the casing to restrict the atmosphere from flowing into the casing. This restricts the temperature of the substrate in the processing unit from partially varying by the atmosphere and temperature distribution from becoming ununiform within a plane of the substrate.
The inflow restricting device may have a guide plate for guiding in a direction away from the transfer port a gas current of the atmosphere flowing from top to bottom.
Further, the inflow restricting device may further have a current regulating plate for regulating in a direction away from the transfer port a gas current of the atmosphere flowing from bottom to top.
Furthermore, the carrier may be structured to have a guide for guiding in a direction, other than the direction of the transfer port, the atmosphere guided by the guide plate. The guide is provided on the carrier side as in the above manner leads to better results.